The present invention relates to a heat storage element for use in heating apparatuses, etc., and an electric heater using the same.
Heretofore, when using a latent heat storage material hermetically sealed in a flexible container, the mouth of the container was sealed under atmospheric pressure, after a solid or liquid latent heat storage material had been filled in the container.
When such a sealing method is utilized and if the latent heat storage material is in granular shape, more than 33% of the volume of the container is occupied by air which is sealed in together therewith. Moreover, as this element is heated, the air inside the container will expand and its proportion will further increase. If any air exists inside the heat storage element, the heat is transferred from outside to the heat storage material through this air layer; therefore, the heat transfer becomes harder than when the air layer does not exist, resulting a longer time being taken before the storing of heat has been accomplished. It is only natural that if the heat storage material and air are concurrently sealed in the heat storage element, the heat storage density per unit volume of the heat storage element will diminish. If the latent heat storage material in liquid state is sealed in a flexible container and the container is to be hermetically sealed, with the air content down, the liquid will come up to the fusing part (the mouth of the container) as the fusing layers are brought together, to be adhering thereon, thus detracting from proper sealing. Although the sealing for housing appears to be proper, the housings are easily opened by a small external pressure. Then it is inevitable concurrently to seal into the container a large amount of air in order to ensure the sealing; as a consequence, the heat storage characteristic is affected, with reduced heat storage density, as in the case of heat storage element having a granular latent heat storage material sealed in. Besides, when this heat storage element and an electric heater element are used in combination, because of the existence of air in the heat storage element, almost no heat is transferred to the heat storage material from the electric heater element part in the neighborhood of the air. Therefore, the temperature of the electric heater element at that part rises very high, sometimes with a risk of burning.